Merck wins FDA approval for a once-vaunted cardio drug

Merck ($MRK) picked up FDA approval for the clot-busting cardio drug vorapaxar, a treatment once billed as a potential warfarin successor before running into some alarming safety issues.

The pill, to be marketed as Zontivity, is a first-in-class inhibitor of PAR-1, stopping the receptor from interacting with thrombin and thus halting platelets from forming blood clots. The drug is approved to reduce risk of heart attack, stroke and other cardiovascular events in patients who have already endured a heart attack or who have peripheral arterial disease. In its pivotal data submitted to the FDA, vorapaxar lowered stroke risk from 9.5% to 7.9% over three years, the agency said.

However, Merck's cardio contender carries some serious bleeding risks, and the FDA has slapped a black-box warning on the drug to advise physicians of the potential for fatal episodes. As expected, vorapaxar is contraindicated for patients who have already had strokes or transient ischemic attack, excising a sizable patient population and dampening sales projections.

The well-traveled treatment was a major factor in Merck's $41 billion buyout of Schering-Plough back in 2009, singled out as a pill with a blockbuster future with the potential to beat out tried-and-cheap warfarin and notch peak sales of up to $5 billion a year. Within three years, however, serious bleeding risks came to light, leading Merck to leave out stroke patients from its FDA application and thereby trim some of vorapaxar's potential market.

But the drugmaker remains confident its cardio drug has a bright commercial future. About 7.6 million Americans have suffered a heart attack, Merck has said, and about 190,000 eventually have a recurrent episode, creating a sizable unmet need.

Meanwhile, the Whitehouse Station, NJ, pharma giant is in the midst of an R&D realignment, which includes a renewed focus on cardiovascular therapies. Alongside the Phase III atherosclerosis drug anacetrapib, vorapaxar was the second late-stage pillar in Merck's thin cardio pipeline, but the drugmaker has since struck up a deal worth up to $2.1 billion with Bayer, signing up to share rights to the pulmonary arterial hypertension treatment Adempas and collaborate on some in-development heart failure candidates.

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